The present invention relates generally to mineral comminution devices, and particularly to conical rock crushers in which an upper frame is held in releasably biased relationship against a fixed main frame.
Conical type rock crushers of the type contemplated for use with the present retention and positioning device include a fixed main frame enclosing a gyrating conical head. The gyrating head defines a lower crushing surface. An upper frame or bowl is held in releasably biased relationship against an upper seat of the main frame, usually by a plurality of coiled springs, fluid power cylinders, or a combination of the two. The bowl includes a bowl liner which defines a normally fixed upper crushing surface. Incoming mineral material is fed between the upper and lower crushing surfaces where it is reduced to a specified size or smaller. Such a crusher is disclosed in commonly-assigned U.S. Pat. No. 4,478,373, which is incorporated by reference herein.
During operation, the bowl is maintained in a biased, contacting relationship to the upper seat, however, in a process known as tramp release, the bowl may lift upon the introduction of uncrushable matter or tramp material with the feed material. Once the tramp material has been passed, the bowl returns to contact the upper seat, usually with a forceful impact which causes high localized stresses, and may in some cases result in damage and failure to the upper seat area or corresponding regions of the bowl.
Attempts at lessening the stresses generated by the shock of the reseating bowl have typically involved the insertion of shock absorbing material between the upper seat and the bowl. One such attempt is disclosed in U.S. Pat. No. 4,773,604, wherein the main frame has a separate upper seat provided with a plurality of annular grooves. A like plurality of rings of resilient material are inserted into the grooves and retained there by compression. The resilient rings are dimensioned to project above the surface of the upper seat and thus form a shock absorbent cushion for the bowl.
However, a significant drawback of such an arrangement is that in some cases, the resilient inserts are not adequately retained within the grooves, and may have the tendency to dislodge during operation. In addition, the shock absorbing material of which the inserts are made has the tendency to collapse or migrate due to the extreme forces generated by the bowl returning to its normal operating position. Another design consideration of such a system is that the machining of the annular grooves may enhance the stress loading on the upper seat caused by the impacting bowl.
Thus, a main object of the present invention is to provide an effective system for absorbing shock generated by the bowl returning to the upper seat.
Another object of the present invention is to provide an upper seat protective device which employs resilient, shock absorbing material in a manner wherein any migration and/or flow of the resilient material under the extreme shock loading generated during crusher operation is accommodated.
Yet another object of the present invention is to provide a shock absorbing system for the upper seat of a conical crusher, which may be readily adapted to existing crushers in the field.